Apparatus and method for monitoring and regulating cryogenic cooling

ABSTRACT

An apparatus and method for monitoring and/or controlling cryogenic cooling by measuring the opacity of the vapor cloud ( 113 ) generated from a cryogenic cooling device ( 112 ). The opacity is determined by measuring the reduction in intensity of a light beam ( 127 ) passed through the vapor cloud ( 113 ). The opacity measurements are used to control an operating parameter of the system, such as the cooling rate of the cryogenic cooling device ( 112 ). The opacity measurements may be normalized to compensate for variables, other than temperature of the workpiece ( 119 ) and cooling rate, which may affect the opacity of the vapor cloud ( 113 ).

This application is the National Stage of International Application No. PCT/US08/74465, filed Aug. 27, 2008, which claims the benefit of U.S. Provisional Application No. 60/968,479, filed on Aug. 28, 2007, which is incorporated herein by reference in its entirety as if fully set forth.

BACKGROUND

The present invention relates to cryogenic spray cooling, which is commonly used in metalworking and other industrial applications that demand cooling to maintain optimal process parameters.

Direct sensing of workpiece and tool surface temperature in metalworking applications is challenging. Due to the fact that both the work and tool are in motion, contact-based temperature measurement is not desirable. Conventional non-contact temperature measurement devices, such as infra-red (IR) sensors and thermometers, are often inaccurate due to measurement errors induced by the reflectivity of the work and tool materials, as well as low radiation levels in the low-temperature range. In applications where cryogenic cooling is used, accurate temperature measurement is of increased importance. Accordingly, a more accurate method of non-contact temperature measurement is needed.

Related art includes U.S. Pat. No. 5,517,842 and PCT Publication No. WO2006/074875A1.

SUMMARY OF THE INVENTION

The present invention comprises an apparatus for a system having a cryogenic cooling component that generates a vapor cloud when operated. The apparatus senses the cooling and sends a signal to a controller that is programmed to set and/or adjust at least one operating parameter of the system.

In one respect, the invention comprises an apparatus for use with a system having a cryogenic cooling component that generates a vapor cloud when operating. The apparatus including a first emitter that is adapted to emit a first light beam at a first intensity. The apparatus further includes a first receiver having a first sensor that is adapted to detect a first sensed intensity. The first sensed intensity being the intensity of the first light beam at the first sensor when the first light beam is directed at the first sensor. The first receiver being adapted to generate a first sensor signal that is a function of the first sensed intensity, and the first emitter and first sensor having a first operating position, where the first emitter and first sensor are positioned and oriented so that the first light beam is directed onto the first sensor and the first light beam passes through the vapor cloud at least once before being received by the first sensor. A controller is also provided and is programmed to set and/or adjust at least one operating parameter of the system based on controller data. When the first emitter and second sensor are in the first operating position, the controller data comprises the first sensor signal.

In another respect, the invention comprises an apparatus for use with a system having a cryogenic cooling component that generates a vapor cloud when operated. The apparatus includes means for determining relative opacity of the vapor cloud and generating data relating to the relative opacity of the vapor cloud and a controller in communication with the means for determining, the controller being adapted to set and/or adjust at least one operating parameter of the system based on the data.

In yet another respect, the invention comprises a method used with a system having a cryogenic cooling component, the method including measuring the relative opacity of a cryogenic vapor cloud, and setting and/or adjusting at least one operating parameter of the system based on the measured relative opacity of the cryogenic vapor cloud.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of the preferred embodiments of the invention will be better understood when read in conjunction with the appended drawings. For the purposes of illustrating the invention, there is shown in the drawings embodiments which are presently preferred. It is understood, however, that the invention is not limited to the precise arrangements and instrumentality shown in the drawings:

FIG. 1 is a first embodiment of a basic cryogenic vapor cloud opacity measurement apparatus, in accordance with the present invention;

FIG. 2 is a second embodiment of a basic cryogenic vapor cloud opacity measurement apparatus, in which the light beam is reflected;

FIG. 3 is a schematic representation of a preferred embodiment of an apparatus for monitoring and regulating cryogenic cooling of a workpiece and roller according to the present invention; and

FIG. 4 is a schematic representation of a second embodiment of an apparatus for monitoring and regulating cryogenic cooling of a workpiece and roller.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is an apparatus for use with a system having a cryogenic cooling component that generates a vapor cloud when operating. Systems that have a cryogenic cooling component may include, but are not limited to, metal rolling and machining operations such as lathe turning, boring, milling, thermal spray coating applications, and food freezing applications.

“Cryogenic vapor” is a suspension of microscopic water ice crystals which forms when water contained in ambient air comes in contact with a cryogenic spray, such as liquid nitrogen (hereinafter “LIN”), gaseous nitrogen, argon and carbon dioxide or a mixture of two or more of these liquids and/or gases. Cryogenic vapor is typically white and opaque or semi-opaque.

During experiments relating to the development of the present invention, it was observed that the amount of “cryogenic vapor” evolving from an area in which a cryogenic spray is being directed onto a substrate, e.g. workpiece and/or tool area and/or part surface and/or other surface of an object to be cooled, was inversely proportional to the surface temperature of the surface onto which the spray was being applied. In all cases observed, a large amount of cryogenic vapor was observed when the substrate (e.g. workpiece, part and/or tool) surfaces were below the desired temperature range (i.e., overcooling) and almost no cryogenic vapor was visible when the workpiece and tool surfaces were above the desired temperature range (i.e., insufficient cooling). It was observed that the “cloud” generated by a large amount of cryogenic vapor was more opaque than a smaller amount of cryogenic vapor. Applicants discovered that the opacity of the vapor cloud could be measured with reasonable accuracy by measuring the drop in intensity of a light beam that is directed through the vapor cloud. The intensity drop is due to dispersion and absorption of the light beam on the solid surfaces of microscopic ice crystals, which form part of a cryogenic vapor cloud. These concepts form the basis for the present invention.

FIG. 1 illustrates a basic apparatus used to measure cryogenic vapor opacity. As can be seen in FIG. 1, a cryogenic cooling device 12 is generating a vapor cloud 13. A light source 23 is positioned to direct a light beam 25 through the vapor cloud 13. In this embodiment, the light source 23 is a laser emitter. A receiver 29 is positioned in the path of the light beam 25 after the light beam 25 has passed through the vapor cloud 13. The receiver 29 has a light sensor 31 that is adapted to detect the intensity 33 of light within the wavelength range of the light beam 25. The light beam 25 has a known initial intensity 27 at the light source 23 and a lower intensity 33 when it reaches the sensor 31 (“sensed intensity”), after passing through the vapor cloud 13. Preferably, the sensor 31 generates an electrical signal that is proportional to the sensed intensity. In this embodiment, the sensor 31 is an optical sensor that generates a signal in the range of 4-20 mA, based on the sensed intensity.

As noted above, the light source 23 is a laser emitter in this embodiment. It should be understood that other emitters could be used. For the purposes of the specification and claims, the terms “emitter” means any device capable of emitting light and is used interchangeably with the term “light source.” Red or green lasers are examples of preferred light sources for the present invention because the vapor cloud opacity results from the dispersion and absorption of the light beam on the solid surfaces of microscopic ice crystals. Such lasers are particularly suitable for the present invention because they are inexpensive, produce a very focused, easy to measure beam of light, and produce a visible light beam, which facilitates proper positioning of the sensor 31. Light sources that emit light at ultraviolet (UV) or infrared (IR) wavelengths could also be used, but are less preferred because they do not produce visible light beams.

FIG. 2 shows an alternate arrangement for the apparatus shown in FIG. 1. In FIG. 2, a reflector 59 is used to re-direct the light beam 25 before being received by the sensor 31. This allows the receiver 29 and sensor 31 to be located in close proximity to the light source 23. As shown, in this configuration, the light beam 25 passes through the vapor cloud 13 twice. Alternatively, the light beam and the reflector could be positioned so that the light beam passed through the vapor cloud once before being received by the sensor (not shown).

The signal generated by the sensor 31 can be advantageously used in a wide variety of applications. For example, the signal could be used (in combination with other process data) to calculate the temperature of a substrate (workpiece or tool or other object) surface, to generate a notification or alarm if the signal indicates a vapor opacity level that is outside of a preferred operating range, or to control one or more process parameters.

FIG. 3 shows an embodiment of one such application, which includes a mill stand in which a workpiece 119 is being drawn through upper and lower rollers 121, 122. The workpiece 119 and rollers 121, 122 are cooled by a cryogenic spray device 112 that generates a vapor cloud 113. In this embodiment, the cryogenic spray device 112 is being directed onto the upper roller 121. Many other configurations are possible, depending upon the metalworking application. For example, the cryogenic spray device 112 could be directed at the surface of the workpiece 119 or could be directed at the intersection of the workpiece and one of the rollers 121, 122.

In this embodiment, the light source 123 and the receiver 129 are located on opposing sides of the workpiece 119 and rollers 121, 122 (similar to the configuration shown in FIG. 1). The light source 123 generates a light beam 125 having an initial intensity 127 (i.e., before it passes through the vapor cloud 113). As in FIG. 1, the light source 123 and a sensor 131 (part of the receiver 129) are positioned so that the light beam 125 from the light source 123 is directed onto the sensor 131 (i.e., an operating position). The sensor 131 generates an electrical signal 135, which is proportional to the intensity 133 of the light beam 125 as it is received by the sensor 131.

In this embodiment, the light beam 125 is a laser and the signal 135 generated by the sensor 131 is a 4-20 mA analog signal.

A controller 137 is programmed to set and/or adjust one or more operating parameters of the system based controller data received from the system. In accordance with the present invention, the controller data preferably includes data concerning the opacity of the vapor cloud 113, which is provided by the signal 135 from the sensor 131. For example, the controller 137 could be programmed to increase the cooling rate of the cryogenic spray device 112 if the signal 135 indicates that there is too little cryogenic vapor. The controller 137 could also be configured to activate an alarm if the signal 135 indicates that opacity of the vapor cloud 113 is outside of a predetermined range. Examples of other operating parameters that the controller could be used to adjust include, depending upon the application of the system, mill/drive load, speeds, and rolling speed.

In order to enable the controller 137 to more accurately set and/or adjust operating parameters, the controller data preferably includes data concerning variables (other than the temperature of the workpiece 119) that may affect the opacity of the vapor cloud 113. For example, the opacity of the vapor cloud 113 is directly proportional to the relative humidity of the air in the vicinity of the cryogenic spray device 112. Therefore, this embodiment includes a relative humidity sensor 145, which generates a signal 147 to the controller 137 that is proportional to the relative humidity of the air in the vicinity of the sensor 145. The controller 137 is programmed to adjust the cooling rate of the cryogenic spray device 112 based on signals 135 and 147.

Airflow in the vicinity of the vapor cloud 113 may also affect the measured opacity of the vapor cloud 113. Assuming all other pertinent variables are kept constant, the measured opacity of the vapor cloud 113 will decrease if airflow in the vicinity of the vapor cloud 113 increases. Airflow can be approximated by measuring the velocity of the workpiece 119 or rollers 121, 122. Accordingly, this embodiment includes a velocity sensor 149, which is configured to measure the velocity of the workpiece 119 and to generate a velocity signal 151. In an alternate embodiment in which the velocity of the workpiece 119 is an operating parameter that is set and/or adjusted by the controller 137, the velocity of the workpiece 119 would serve a dual role—being both an operating parameter and controller data.

In order to provide maximum operational flexibility, the cryogenic spray device 112 preferably allows for precise and simple adjustment of its cooling rate. Examples of cryogenic spray devices having this capability are disclosed in U.S. patent application Ser. No. 11/846,116, filed Aug. 28, 2007, which is hereby incorporated by reference as if fully set forth. It should be understood, however, that the concepts of the present invention could be applied to any type of cryogenic cooling device that generates a vapor cloud.

In this embodiment, the cryogenic spray device 112 includes a liquid nitrogen (“LIN”) feed line L1, two throttling gas lines G1, G2 (located at opposing ends of the cryogenic spray device 112) and a gas purge line Gp. The LIN feed line L1 is preferably connected to a pressurized source of LIN (not shown). Similarly, the throttling gas lines G1, G2 and purge gas line Gp are preferably connected to a pressurized source of gaseous nitrogen. As described in greater detail in U.S. patent application Ser. No. 11/846,116, filed Aug. 28, 2007, which is hereby incorporated by reference in its entirety as if fully set forth, the cooling rate and cooling profile of the cryogenic spray device 112 (i.e. the flow rate of LIN through the cryogenic spray device 112) can be precisely controlled by adjusting the gas pressure on the throttling gas lines G1, G2. In addition, the purge line Gp can be used to purge and clean the cryogenic spray device 112 and/or the surface at which the cryogenic spray device 112 is directed (in this embodiment, roller 121).

As noted above, the opacity of the vapor cloud 113 can be correlated with the temperature of the workpiece 119. Therefore, the controller 137 can use the signal 135 to set and/or adjust operating parameters of the system in which the controller 137 is used which are normally set and/or adjusted based on the temperature of the workpiece 119.

FIG. 4 shows an alternate configuration for a vapor cloud opacity measuring apparatus, which comprises a light source 223 that generates a light beam 225 having an initial intensity 227 (i.e., before it passes through the vapor cloud 213) and a sensor 231, which is part of a receiver 229. As in the embodiment shown in FIG. 2, the light source 223 and sensor 231 are positioned so that the light beam 225 passes through the vapor cloud 213, is reflected on the surface of a roller 221, passes through the vapor cloud 213 a second time, and is then received by the sensor 231. This configuration enables the light source 223 to be positioned adjacent the sensor 231 and, if desired, to be provided as a unitary assembly. The reflection of the light beam 225 against the surface of a roller 221 is particularly useful in the industrial cold and temper rolling operations where a near mirror roller finish is required.

This configuration also enables the vapor cloud opacity measurement apparatus to be located at any desirable position along the length of the cryogenic spray device 212. In addition, multiple vapor cloud opacity measurement apparatuses (not shown) could be positioned along the length of the cryogenic spray device 212. Such a configuration would enable more precise measurement and control of the temperature of the workpiece 219, to the extent that it varies along its width. For example, if higher vapor opacity was detected at the edges of the workpiece 219 than at its center, the cryogenic spray device 212 could be adjusted to provide more cooling to the center of the workpiece 219 and less cooling to the edges of the workpiece 219. This functionality is highly desirable in the majority of metal rolling operations, where workpiece and roller edges tend to be overcooled resulting in numerous production and product quality problems.

If multiple vapor cloud opacity measurement apparatuses are to be used along the length of a cryogenic spray device 212, it is preferable that the cryogenic spray device 212 be adapted to provide a non-linear cooling profile (i.e., the ability to provide different cooling rates along the length of the cryogenic spray device 212). Examples of this type of cryogenic spray device are disclosed above in connection with the embodiment shown in FIG. 3, as well as in U.S. patent application Ser. No. 11/846,116. It should be understood, however, that the concepts of the present invention could be applied to any type of cryogenic cooling device that generates a vapor cloud.

Other than the configuration of the vapor cloud opacity measurement apparatus, the embodiment shown in FIG. 4 includes all of the components (including a controller) of the embodiment shown in FIG. 3. In the interest of simplicity, many of these components are not shown in FIG. 4.

In this embodiment, a second light source 261 and a second receiver 263 are provided to supply the controller (not shown) with controller data concerning the reflectivity of the roller 222. The second light source 261 and sensor 269 are positioned so that the light beam 265 is reflected on the surface of a roller 222 and is received by the sensor 269, but does not pass through any portion of a vapor cloud. The receiver 263 generates a signal 273, which is proportional to the intensity of the light beam 265 when it is received by the sensor 269.

The signal 273 enables the controller to “normalize” the signal 235 to compensate for changes in reflectivity of the rollers 221, 222. In addition, the signal 273 could be used to determine if the reflectivity of the roller 222 is outside a predetermined operating range, which may be an indication of excess water condensation, surface oxidation, deposit, and/or dust buildup on the roller 222.

It is recognized by those skilled in the art that changes may be made to the above-described embodiments of the invention without departing from the broad inventive concepts thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed but is intended to cover all modifications which are in the spirit and scope of the invention. 

1. An apparatus for use with a system having a cryogenic cooling component that generates a vapor cloud when operating, the apparatus comprising: a first emitter that is adapted to emit a first light beam at a first initial intensity; a first receiver having a first sensor that is adapted to detect a first sensed intensity, the first sensed intensity being the intensity of the first light beam at the first sensor when the first light beam is directed at the first sensor, the first receiver being adapted to generate a first sensor signal that is a function of the first sensed intensity, the first emitter and first sensor having a first operating position in which the first emitter and first sensor are positioned and oriented so that the first light beam is directed onto the first sensor and the first light beam passes through the vapor cloud at least once before being received by the first sensor; and a controller that is programmed to set and/or adjust at least one operating parameter of the system based on controller data, the controller data comprising the first sensor signal.
 2. The apparatus of claim 1, wherein the at least one operating parameter comprises a cooling rate of the cryogenic cooling component.
 3. The apparatus of claim 1, wherein the at least one operating parameter comprises an alarm that is activated if the first sensor signal indicates that opacity of the vapor cloud is outside of a predetermined range.
 4. The apparatus of claim 1, wherein the first light beam comprises a visible laser.
 5. The apparatus of claim 1, further comprising a sensor group comprising at least one parameter sensor, each of the at least one parameter sensor being adapted to measure a parameter, other than the temperature of a substrate on which the cooling component is being applied, that may affect the opacity of the vapor cloud and to generate a parameter sensor signal that is a function of the parameter being sensed by the at least one parameter sensor, wherein the data further comprises the parameter sensor signal from each of the at least one sensor.
 6. The apparatus of claim 1, further comprising a third sensor adapted to measure relative humidity of ambient air in the vicinity of the vapor cloud and adapted to generate a third signal that is a function of the measured relative humidity and wherein the controller data further comprises the third signal.
 7. The apparatus of claim 1, further comprising a fourth sensor adapted to determine the velocity of a substrate as it moves past the cryogenic cooling component and adapted to generate a fourth signal that is a function of the measured velocity and wherein the controller data further comprises the fourth signal.
 8. The apparatus of claim 1, first emitter and first receiver are positioned so that the light beam is reflected by a first surface before being received by the first sensor.
 9. The apparatus of claim 8, wherein the first sensor is positioned adjacent to the first emitter.
 10. The apparatus of claim 8, further comprising: a second emitter that is adapted to emit a second light beam at a second initial intensity; a second receiver having a second sensor that is adapted to detect a second sensed intensity, the second sensed intensity being the intensity of the second light beam at the second sensor when the second light beam is directed at the second sensor, the second receiver being adapted to generate a second sensor signal that is a function of the second sensed intensity, the second emitter and second sensor having a second operating position in which the second emitter and second sensor are positioned so that the second light beam is directed onto the second sensor, the second light beam is reflected by either the first surface or a second surface before being received by the second sensor, and the second light beam does not pass through the vapor cloud at least once before being received by the second sensor; and wherein the controller is programmed to set and/or adjust the at least one operating parameter of the system based on the controller data and when the first emitter and second sensor are in the first operating position and the second emitter and second sensor are in the second operating position, the controller data comprising the first sensor signal and the second sensor signal.
 11. The apparatus of claim 10, wherein the first sensor is positioned adjacent to the first emitter and the second sensor is positioned adjacent to the second emitter.
 12. An apparatus for use with a system having a cryogenic cooling component that generates a vapor cloud when operated, the apparatus comprising: means for measuring the relative opacity of at least a portion of the vapor cloud; and a controller in communication with the means for measuring, the controller being adapted to set and/or adjust at least one operating parameter of the system based on the relative opacity of the at least a portion of the vapor cloud.
 13. The apparatus of claim 12, wherein the at least one operating parameter comprises a cooling rate of the cryogenic cooling component.
 14. The apparatus of claim 12, wherein the at least one operating parameter comprises an alarm that is activated if the first sensor signal indicates that opacity of the at least a portion of the vapor cloud is outside of a predetermined range.
 15. A method used with a system having a cryogenic cooling component, the method comprising: determining the relative opacity of at least a portion of a cryogenic vapor cloud; and setting and/or adjusting at least one operating parameter of the system based on the relative opacity of the at least a portion of the cryogenic vapor cloud.
 16. The method of claim 15, wherein determining the relative opacity of the at least a portion of the cryogenic vapor cloud further comprises: directing a first light beam through at least a portion of a cryogenic vapor cloud, the first light beam having a first initial intensity; and measuring the intensity of the first light beam after it has passed through the at least a portion of a cryogenic vapor cloud, the measured intensity comprising a first sensed intensity.
 17. The method of claim 16, wherein determining the relative opacity of at least a portion of the cryogenic vapor cloud further comprises: reflecting the first light beam on a first surface before measuring the intensity of the first light beam.
 18. The method of claim 17, wherein determining the relative opacity of at least a portion of the cryogenic vapor cloud further comprises: measuring the intensity of a second light beam after it has been reflected on one of the first surface or a second surface without passing through any portion of a cryogenic vapor cloud, the measured intensity comprising a second sensed intensity; and comparing the first sensed intensity to the second sensed intensity.
 19. The method of claim 16, wherein determining the relative opacity of at least a portion of the cryogenic vapor cloud further comprises: reflecting the first light beam on a first surface before measuring the intensity of the first light beam.
 20. The method of claim 15, wherein the setting and/or adjusting step further comprises: setting and/or adjusting a cooling rate of the cryogenic cooling component based on the relative opacity of the at least a portion of the cryogenic vapor cloud.
 21. The method of claim 16, wherein: setting and/or adjusting the cooling rate of the cryogenic cooling component comprises setting and/or adjusting a non-linear cooling profile of the cryogenic cooling component based on the relative opacity of at least a portion of the cryogenic vapor cloud; and determining the relative opacity of at least a portion of the cryogenic vapor cloud comprises measuring the relative opacity of a cryogenic vapor cloud at a plurality of locations. 